Zn/Y-and Cd/Y-zeolites were found to be much more active for the formation of acetonitrile from ethene and ammonia than Al2O3 and H/Y-zeolite. Although Zn or Cd/Al2O3 showed the higher activity than Al2O3 itself, Y-zeolite was superior as a support to Al2O3. The partial pressure dependence of NH3 on Zn/Y-zeolite was different from that on Cd/Y-zeolite. The reaction of ethylamine over Zn/Y and Cd/Y-zeolites was performed, since formation of a very small amount of ethylamine was observed during the reaction between ethene and ammonia. However, the amount of acetonitrile formed from ethylamine was very small on Zn/Y-zeolite. The amount of ethylamine rapidly decreased with reaction time. On the other hand, an induction period was observed on the formation of acetonitrile over Zn/Y-zeolite. The Cd/Y-zeolites were found to be almost inactive for the formation of acetonitrile from ethylamine. On the basis of the results obtained, the main reaction route for the acetonitrile formation is thought to be different from the route through the formation of ethylamine.